Oh, much more than that. You need to memorise the layouts of all 16 timezones and be able to flip them upside down and left to right in your head .

Truly wonderful game though. When I was about 15 I spent a large percentage of my waking hours over an entire summer holiday playing one game a day of this trying to beat my high score. Got up to about 300k points. A few years back I spent a few weeks re-learning it and then managed to push my score up to about 450k, although the Automation crack looks to have a bug in it that costs at least 15k points (and, concomittantly, 15 extra lives).